The present invention generally relates to telecommunication apparatuses and more particularly to a telecommunication apparatus such as a telephone apparatus, including a portable radio telephone apparatus, that is capable of controlling an audio output level adaptively in response to a noise level in the environment.
When using a telecommunication apparatus such as a telephone apparatus in a noisy environment, there are cases in which the audio output from the telephone apparatus is difficult to comprehend because of the noise. In order to deal with this problem, there are telephone apparatuses equipped with a manually operative switch such that the user can manually increase or decrease the audio output level of the telephone apparatus in accordance with the noise level of the environment. Further, there are proposals to achieve such a control of the audio output level of the telephone apparatus adaptively in response to the noise level of the environment.
For example, Japanese Laid-Open Utility Model Publication 5-6954 describes a telephone apparatus that carries out a measuring of the noise level in an interval where there is no speech. Thereby, the audio output level of the telephone apparatus is adjusted in response to the detected noise level.
However, the foregoing proposal cannot adapt to a change of the noise level that may occur during the speech, and the audio output level may not be optimum with regard to the real background noise level. Further, the foregoing proposal uses a separate microphone dedicated for the noise level detection, while use of such a separate microphone increases the cost of the telephone apparatus.